構造変化を考慮した力学模型によるガラス状高分子の降伏過程のモデル化

抄録

The rate analysis of steady plastic flow in glassy polymers has verified that the structure of the polymers is changed into a liquid-like structure during the yield process. This result motivated us to develop a mechanical model which predicts the stress-strain curve for glassy polymers. The model is composed of a dashpot and two elastic springs, where the viscosity of dashpot is a single parameter quantifying the structural transition and is approximated by a simple mathematical equation decreasing with increasing strain. Using this model, stress-strain relations were simulated for poly (methyl methacrylate) and poly (vinyl chloride) under uniaxial constant-rate tension and compression. The model reproduced successfully the experimental stress-strain curves over a wide range of temperature and strain rate for each case. This led to a conclusion that at a uniaxial constant deformation rate the structural change in the glasses is mainly governed by strain. Moreover, the optimum equation for the internal viscosity determined by the simulation indicated that the degree of structural change is closely related to both the yield strain and the strain range in the lower yield state.